On Mercury Diffusion from Artisanal Gold Mining:

Transcription

1 On Mercury Diffusion from Artisanal Gold Mining: A Case Study from Talawaan Watershed, North Sulawesi, Indonesia Markus T. Lasut Faculty of Fisheries and Marine Science, Sam Ratulangi University, Manado, North Sulawesi, Indonesia Yoshiaki Yasuda Natural Sciences Section, National Institute for Minamata Disease, Minamata City, Kumamoto, Japan NIMD Forum, Feb 2010 Lasut & Yasuda 1

2 Mercury (Hg) Hg o Hg +2 MeHg elemental inorganic Organic Form Toxicity Transformation NIMD Forum, Feb 2010 Lasut & Yasuda 2

3 Scope of the study Hg discharge Biota Food Chain Fish Hg application (e.g. gold mining) Sediment Impacts? NIMD Forum, Feb 2010 Lasut & Yasuda 3

4 Indonesia North Sulawesi Talawaan Watershed Jakarta Talawaan Watershed North Sulawesi NIMD Forum, Feb 2010 Lasut & Yasuda 4

5 Talawaan Watershed Gold Mining Area Daily activities: Fishing Fish farm Bathing Washing Etc. Talawaan River Kima River Talawaan Watershed (34,000 Ha) Bailang River Artisanal Gold Mining Area NIMD Forum, Feb 2010 Lasut & Yasuda 5

6 Artisanal Gold Mining Activity NIMD Forum, Feb 2010 Lasut & Yasuda 6

7 Artisanal Gold Mining Activity Economic Aspect Good prospect, since many villagers are employed and earn money from gold selling It is estimated that a trommel unit produces 6 to 10 g gold/day (average: 6 g) If the price of gold is 50,000 rupiahs/g, so for 500 trommel units produce 150 million rupiahs per day or 30 billion rupiahs per year (1 Yen = 100 rupiahs) It is a big money for a small district NIMD Forum, Feb 2010 Lasut & Yasuda 7

8 Hg Discharge Environmental Concerns Tailings The mercury is liberated to water and public facilities through rivers and canals The amount of mercury released is still immeasurable Amalgam released from the process Simple gravity technique NIMD Forum, Feb 2010 Lasut & Yasuda 8

9 Hg Discharge Environmental Concerns If there are 500 units of trommels operates everyday; and 1 to 2 kg of Hg per unit per day is used; 200 days of working day/year; so the Hg consumption is 200 ton/year. Following is the estimation of Hg production: - Hg used for amalgamation process in trommel: 500 units x 2 kg= 1000 kg - Hg releases to atmosphere (through burning amalgam): if, a trommel produces 87.7 g of amalgam per day with g of Hg vapor and 24.8 g of gold, and twice a day of production, so the estimation of Hg released to the atmosphere per day for 1 unit: 2 x g = g; for 500 units: 500 x g = kg NIMD Forum, Feb 2010 Lasut & Yasuda 9

10 Talawaan Watershed Gold Mining Area (After 2004) NIMD Forum, Feb 2010 Lasut & Yasuda 10

11 Objective of Study To evaluate distribution of methylmercury (MeHg) derived from anthropogenic metallic mercury usage of artisanal gold mining NIMD Forum, Feb 2010 Lasut & Yasuda 11

12 Location of Sampling TL: Talawaan River KM: Kima River BL: Bailang River Green line triangle indicates the area of gold mines NIMD Forum, Feb 2010 Lasut & Yasuda 12

13 Samples and methods Samples Sediments Biota THg Hg analyzer MeHg gas chromatograph with ECD detector after extracted by dithizone-sodium sulfide extraction method NIMD Forum, Feb 2010 Lasut & Yasuda 13

14 RESULTS NIMD Forum, Feb 2010 Lasut & Yasuda 14

15 THg Control= 5.8 ng/g NIMD Forum, Feb 2010 Lasut & Yasuda 15

16 MeHg Control= 0.22 ng/g NIMD Forum, Feb 2010 Lasut & Yasuda 16

17 MeHg ng/g MeHg ng/g MeHg ng/g MeHg on THg (Talawaan River) THg - MeHg MeHg on THg (Kima River) MeHg on THg (Bailang River) A y = x y = x R 2 = B R 2 = C y = x R 2 = THg ug/g THg ug/g THg ug/g Talawaan River Kima River Bailang River NIMD Forum, Feb 2010 Lasut & Yasuda 17

18 MeHg ng/g MeHg ng/g LOI - MeHg MeHg-Ig TL KM BL TL r=0.79 BL r=0.64 KM r=0.42 R 2 = Talawaan River 15 Kima River 10 Bailang River 5 0 R 2 = R 2 = LOI NIMD Forum, Feb 2010 Lasut & Yasuda 18

19 Hg in sediment: Methylation & Demethylation Methylation/demethylation processes in riverine system Hg o Hg +2 MeHg elemental inorganic Organic Discharging from the gold mining Found in sediment samples NIMD Forum, Feb 2010 Lasut & Yasuda 19

20 Conclusion Mercury released as metallic mercury from artisanal gold mining was distributed along the watershed area in form of inorganc and organic (methyl) mercury Highest concentration of mercury was found at the area close to the mining activity Since there was no methylmercury source in the area, the released metallic mercury was found methylated in sediment. NIMD Forum, Feb 2010 Lasut & Yasuda 20

21 Acknowledgement We appreciate and give special thank to: All personals in Organizing Committee of NIMD Forum 2010 NIMD Forum, Feb 2010 Lasut & Yasuda 21

22 On Mercury Diffusion from Artisanal Gold Mining: A Case Study from Talawaan Watershed, North Sulawesi, Indonesia M. T. Lasut 1, Y. Yasuda 2 1: Faculty of Fisheries and Marine Science, Sam Ratulangi University, North Sulawesi, Jl. Kampus Unsrat Bahu, Manado 95115, Sulawesi Utara, Indonesia 2: National Institute for Minamata Disease, Hama, Minamata City, Kumamoto , Japan Artisanal gold mining activity using mercury-amalgamation technique for gold recovery could be the source of methylmercury distributed in the area where such activity presents. It is because the metallic mercury used by the activity released to the environment can be transformed to inorganic and organic forms. To understand such condition, this study was conducted; aimed to evaluate the distribution of methylmercury (MeHg) derived from anthropogenic metallic mercury usage of artisanal gold mining in Talawaan Watershed, North Sulawesi Province, Indonesia. In this study, methylmercury (MeHg) as well as total mercury (THg) in sediments of three rivers, [Talawaan River (TR), Kima River (KR), and Bailang River (BR)] in the watershed originated from the area where a lot of small-scaled gold mining is present was determined. The results showed that geometric means of sediment THg and MeHg concentrations in each river are 0.31 µg/g and 0.92 ng/g in TL, 0.04 µg/g and 0.59 ng/g in KR, and 0.04 µg/g and 0.43 ng/g in BR. The maximum values for THg and MeHg were both detected in TR at close to the mining area, 3.25 µg/g and 9.20 ng/g. The distributions of MeHg were highly correlated with those of THg, which intimates MeHg was generated from the metallic mercury derived from the artisanal gold minings waste materials. In addition, MeHg concentrations in sediment samples were correlated with amounts of ignition loss. It can be concluded that mercury released as metallic mercury from artisanal gold mining using mercury amalgamation-technique was distributed along the watershed area in form of methylmercury, which high concentrations were found close to the mining activity. Since there was no methylmercury source in the area, the released metallic mercury was found methylated in sediment.